Paper bags, e.g., for packaging cement or other powdered or granular materials of high solidity, are manufactured of multilayered tube sections, the individual layers of which are glued together at their edges during the formation of the tube, wherein the individual layers lie on top of one another at the ends of the paper bags such that their cut edges are aligned (straight cut) or preferably only overlap one another in a partially staggered formation, so that the layers are also glued together individually during the formation of the base of the bag.
Rational machine requirements make it necessary that the equipment be able to manufacture tube sections of different formats with a staggered arrangement of the individual paper layers. In order to realize this desired variability of the format in so-called "tube machines," the distances between the transverse perforations that determine the length of the tube sections must be altered in the individual paper layers, and it must also be possible to correspondingly adapt the distances between the transversely extending transverse gluing strips.
Although it is inconsequential if certain differences exist between the circumferential speed of the transverse gluing bars and the moving speed of the paper web such that certain smearing of the applied glue occurs due to the relative speed, such differences between the circumferential speed of the perforating knives and the moving speed of the paper webs cannot be accepted because these relative speeds may lead to tearing of the transverse perforations and consequently a separation of the paper web.
In order to make it possible to provide paper webs in tube machines with transverse perforations at different distances, it is known to drive the rotating perforating knives via transmissions with varying velocity ratio in such a way that the paper web is advanced at a speed that differs from the circumferential speed of the perforating knife within the region in which the perforating knife is not in contact with the paper web, while the circumferential speed of the perforating knife essentially is identical to the moving speed of the paper web at the time at which the perforating knife comes in contact with the paper web. Such transmissions with varying velocity ratio include slider crank gears which, due to their nonuniformity, are exposed to rapid accelerations and decelerations during their revolutions, so that, due to the resulting inertial forces, the machine operates with less power in order to maintain the inertial forces created within permissible limits.
U.S. Pat. No. 2,013,086 discloses a tube machine of the initially mentioned type in which the perforating knives that produce the transverse perforations are fastened onto arms that may be adjusted relative to the shafts carrying the perforation knives in the radial direction. These radially adjustable perforating knives may be continuously driven at the same circumferential speed as the moving speed of the paper webs by correspondingly altering the axial distances between the shafts carrying the perforating knives, so that no nonuniformities that could limit the operating speed of the tube machine due to the inertial forces are present in the drive unit. However, the adjustment of different formats in this known machine is limited due to the fact that, when reducing the distance between the transverse perforations, the arms carrying the perforating knives can only be adjusted radially inward to such an extent that their outer ends that protrude beyond the shafts do not come into contact with the paper web and damage it. Consequently, this known tube machine only allows a variability in the format to such an extent that the largest lengths are approximately twice as large as the smallest lengths because otherwise the ends of the arms that are equipped with the perforating tool would come into contact with the passing paper webs if the distances between the perforations would be reduced additionally. Consequently, this known tube machine does not fulfill today's demands for a variable format because it is required to manufacture tube sections, the smallest lengths of which approximately correspond to one-sixth to one-eighth of the largest length.